TITLE:
Incoherent Oscillations Accompanying Charge Separation in Photosynthetic Reaction Centers
AUTHORS:
A. G. Yakovlev, V. A. Shuvalov
KEYWORDS:
Photosynthesis; Charge Separation; Reaction Center; Electron Transfer
JOURNAL NAME:
Open Journal of Applied Sciences,
Vol.3 No.3B,
October
10,
2013
ABSTRACT: Early events of charge separation in reaction centers (RCs) of
bacterial photosynthesis are modeled by kinetic equations with time-dependent
rate constants. An illustrative case of regular motion along a “slow”
coordinates leading to oscillations in the kinetics is examined. Different
schemes of charge separation are investigated. A good fitting of experimental
kinetics of native Rba. sphaeroides RCs is achieved in the five states
model P*1BAHA↔P*2BAHA↔I↔P+HA↔P+BA with two
excited states BAHA and BAHA and three charge separated
states I, P+HA and P+BA (P is a primary
electron donor, bacteriochlorophyll dimer, BA and HA are
an electron acceptor, monomeric bacteriochlorophyll and bacteriopheophytin in
active A-branch, respectively). In the model only the first excited state is
directly populated by optical excitation. The emission of the two excited
states is assumed to be at 905 and 940 nm, respectively. The intermediate state
I is assumed to absorb at 1020 nm as well as the P+HA state. The model explains the deep
oscillations in the kinetics of the stimulated
emission and of the absorption. In
the simpler schemes without the I state or with only one excited state the
accordance with the experiment is achieved at unreal parameter values. A
possible nature of the I and BAHA states and a possible
incoherent nature of the oscillations are discussed.